Monday, July 28, 2008

Recent flower sightings

Lots of species are now in flower, and we are not even into aster/goldenrod season yet. Although we could use a bit more rain, most of the deep-rooted prairie plants are still in good shape from all the June/early July rains.

Purple prairie clover (Dalea purpurea) is one of those plants so outlandishly colorful that it is hard to believe it is a product of nature. Although primarily a prairie species, the photo shown here was taken in an open savanna area.

We had purple prairie clover originally only on one of our remnants (Unit 1), and we collected seed to plant in other parts of the Conservancy. Now we find it in small amounts in most of our prairie and savanna remnants, as well as in the former ag fields that we have planted to prairie. It took about 5 years to get established well from seed. A related species, white prairie clover (Dalea candida), flowers earlier and is almost finished. It is a more robust species and forms fairly large clumps. The two species can be distinguished in the vegetative state by the sizes of the leaves.

Nodding wild onion (Allium cernuum) is another prairie/savanna species that is now in full flower. According to Cochrane and Iltis, this is rare but locally abundant in southern Wisconsin, and is often found on areas with dolomitic rocks, such as ours. I see this plant more commonly in savannas than prairies, although this may be because in the prairies it may be hidden among the tall grasses. Our plants developed from seed that was brought in from another southern Wisconsin site.

The third species here, whorled milkweed (Asclepias verticillata) is more common than the other two. It is native to the Conservancy and grows all over the south-facing slope.

At first glance it doesn't even look like a milkweed, but a close examination of its small flowers shows otherwise. It forms small and slender pods that are definitely milkweed in structure. It is a clonal species, forming largish patches on the dry prairies. There are some nice patches in bloom right now in the road cut along Pleasant Valley Road (where this photo was taken).

When we set up our forbs garden we planted all the milkweed species for which seeds were available. We were not aware of whorled milkweed's clonal growth habit and were surprised to find it spreading across the whole garden. It even sent runners under the black plastic sheeting we were using for weed control and set up housekeeping in adjacent rows. We had to knock it back by pulling all these outliers.

Among other habitats, we have whorled milkweed growing right out of the dolomitic rocks at the top of Unit 6, more or less surrounding the Aldo Leopold bench. In that habitat single plants grow right out of cracks in the rock where small amounts of soil have accumulated. There it is definitely not clonal, since there is no soil for the rhizomes to spread through.